1. Field of the Invention
This invention relates to a silicone emulsion composition, and more particularly to a silicone emulsion composition having a good dilution property and good stability, and useful as an anti-foaming agent and so forth.
2. Description of the Prior Art
Aqueous emulsions of silicone are widely used in various purposes as anti-foaming agents, foam stabilizers, release agents, water repellents and so forth, but in any instances the emulsions are required to be readily diluted with water, to be stable, and, in particular, to have a dilution stability.
In instances in which the silicone emulsions are used as anti-foaming agents, inorganic fine powders such as finely powdered silica are added to enhance anti-foaming properties. However, the addition of inorganic fine powders may sometimes result in an extremely worsened stability of emulsions. For example, the finely powdered silica may thicken silicon oil used, depending on content thereof, to cause creaming, or the finely powdered silica may be sedimented when emulsions are diluted. It is also known that heating the emulsions to 60.degree. to 80.degree. C. may destroy them, thus promoting the above phenomena such as creaming and sedimentation of finely powdered silica.
To improve the stability of silicone emulsions, a variety of emulsions have been proposed. There have been proposed, for example, a method in which a sucrose fatty acid ester, a sorbitan fatty acid ester and a glycerol fatty acid ester are used in combination [Japanese Patent Publication (KOKOKU) NO. 7335/1983], and a method in which a polyglycerol fatty acid ester is used in combination with a lipophilic emulsifying agent such as a sorbitan fatty acid ester or glycerol fatty acid ester [Japanese Unexamined Patent Publication (KOKAI) No. 262827/1985]. These, however, have been unsatisfactory in view of the stability and dilution property of the resulting silicone emulsion.
Shin-Etsu Chemical Co., Ltd. discloses in Japanese Unexamined Patent Publication (KOKAI) No. 277110/1987 than an emulsion comprising a lipophilic emulsifying agent with an HLB of from 8 to 20 and a lipophilic emulsifying agent with an HLB of from 2 to 7 which are mixed to have an HLB value of from 3 to 19 can effectively improve the stability and dilution property of silicone emulsions.